Request a Ring Sizer from Bluenile.com.
Delivered to your door.
Get the right size the first time by requesting a plastic ring sizer. To order click on the link above and select your preferred delivery method - Rich + foolish person (Fedex $15) or Ozbargainer (free).
Mine has been invaluable (and free) for ordering rings. got the correct size ring when ordering online 3 times.
I know my ring size already - zero